What does the word hairbreadth mean?

Usage examples for hairbreadth

  1. I drew it out and compared it, and perceived that there was not a hairbreadth of difference. – Bagh O Bahar, Or Tales of the Four Darweshes by Mir Amman of Dihli
  2. I passed all the tests, though by a hairbreadth. – Autobiography of a YOGI by Paramhansa Yogananda